The invention relates to a decorative film.
There is a known way of producing interior trim panels for automotive vehicles by connecting dimensionally stable supporting parts and preformed surface layers (decorative films) in special foaming tools by a layer of foam being formed (foam backing). Above all dashboard trims, door interior trim panels and passenger seats are currently manufactured in this manner. The dimensionally stable supporting parts can here consist of any materials (wood-fibre material, sheet metal), by preference however supporting parts formed from injection-moulded or pressed thermoplastics are used. The preformed surface layers can be socalled. “slush skins”, i.e. moulded skins produced by sintering or a slip process in special tools, predominantly from PVC materials (see for example DE 39 32 923 A1). Skins produced by other methods from thermoplastics or thermoplastic elastomers, such as e.g. thermoformed PVC films or sprayed polyurethane skins are also usual. The invention can also be applied to skins which have a multi-layered structure, at least the inner layer of the skin, which is later in contact with the foam, having to consist of a thermoplastic material. The production and processing of skins from suitable material for the mentioned applications are familiar to the expert in this field.
Increasingly, vehicle interior trim panels have areas behind which airbags are arranged, which however are not intended to be recognised. In order to ensure defined tearing open of the decorative film in the event of the release of the airbag, it is usual to weaken the outline of the opening area of the airbag in the film, for example by scoring or laser perforation. Relevant methods are known to the expert and are not the subject matter of this document.
The notch produced e.g. by scoring—generally the cross-sectional weakening—is, so that it remains invisible, naturally introduced into the rear side of the decorative film, i.e. facing the foam backing. During the application of the foam backing, therefore, the expanding foam can penetrate into the weakening notch and bond it together again. The defined tearing forces, predetermined by the weakening, of the break line in the decorative film are thus again undefined, which means the behaviour of the tearing area of the airbag when the latter is released can no longer be predicted with the necessary reliability. A further problem arises from the fact that at the points at. which the notches are located, a diffusion of plasticisers from the decorative film into the foam backing is promoted. The durability of the physical values of the break line can be impaired by this; but also discoloration of the decorative film on the visible side cannot be excluded in the long term. In the utility model DE 298 21 409, to solve the problem of diffusion it is proposed to seal the area of the weakening notch by a protective varnish: if however a strongly adhesive protective varnish is used, which is necessary for effective sealing, bonding together of the weakening notch must also be reckoned with. In addition, a further method step is required which can only be automated with difficulty.